The invention relates to a method for opening threaded joints of drilling equipment by striking the drilling equipment with the percussion device of a rock drilling rig, the method comprising measuring vibration originating from the drill rod during striking and analysing the measured vibration according to a predefined principle for the purpose of determining whether the threaded joints have opened.
The invention further relates to an apparatus for opening threaded joints of drilling equipment by striking the drilling equipment with the percussion device of a rock drilling rig, the apparatus comprising a control device for controlling the rock drilling rig and having a measuring device for measuring vibration originating from the drill rod during striking and analysing means analysing the measured vibration according to a predefined principle for the purpose of determining whether the threaded joints have opened.
When drilling long holes into rock or ground, drill rods are used in which several threaded drill rods are connected together in succession. During drilling, the threads tighten due to both rotating torque and impacts directed to them by the percussion device and stress waves generated as a result of the impacts, and in practice, it is generally not possible to open them with just a rotating motor.
As known, this problem has usually been solved in such a manner that the operator has, after the drilling of the hole has ended, struck the drill rods with the percussion device while they are not under feed force, whereby a suitable number of impacts have loosened the threads. The operator does this by experience and usually stops the striking when hearing a certain type of noise or vibration from the drill rod.
In practice, a problem arises herein from the fact that it is difficult for the operator to detect the loosening of the threads and it does not always succeed the first time. A problem is that unnecessary striking after the threads are already open wears and may even damage the drill rods. Further, the fact that the operator has to do this manually prevents automatization.
Attempts of different type have been made to provide automated drill rod opening and thread openness detection. These are described in publications EP1671011, JP56966/1986, and JP1864566, for example. However, the solutions presented therein are not completely reliable in practice.
One known solution also uses timers to try to control the duration of striking. However, this is not completely reliable, because the time required for striking depends on the drilling parameter values, rock conditions, and even the specific rock drilling rig, for instance. Thus, the striking time varies considerably, and it is difficult to determine a suitable value. Correspondingly, in known automated striking solutions, the result is entirely independent of the operation and accuracy of the equipment, which is not sufficient in practice.